Contents |
Introduction
What are Commensal Rats?
- Norway rat (Rattus norvegicus) – brown or sewer rat
- Roof rat (Rattus rattus) - black, fruit or wharf rat
Identification
Roof rats range in color from black to gray or tan with a lighter belly. Norway rats are reddish-brown in color and are typically heavier than a roof rat. The length of the tail in a Norway rat is shorter than the length of the head and body together. The tail is also dark on top and light underneath. Roof rats have tails that are dark and are longer than the head and body of the rat. Roof rats prefer areas off the ground and are good climbers. They prosper in attics, roof spaces, and ornamental shrubbery.
Roof rats generally enter buildings from overhanging trees or power lines. Norway rats are burrowers and thrive in environments where there is clutter or garbage. They burrow along foundations and under debris. They are good swimmers and may enter buildings through plumbing access points. The home range of these rats may be as much as 50 yards.
General Information
The best method for managing rats is exclusion. Rodents only need a 1/2 inch opening to access an area. While inspecting, listen for scratching, look for droppings, damage, urine (with a black light), and rub marks. Rodents will forage on a variety of items, so sanitation in addition to exclusion is critical. Rodents can cause damage by chewing wood and other items. They have also been known to start fires by gnawing on electrical wires. They carry many different kinds of diseases and bacteria that can lead to food poisoning. Take precaution when removing nest material, droppings, or remains. Rats are active at night. If they are seen during the day there is likely a large population, scarcity of food, or illness within the population. They defecate wherever they go, so droppings will be spread across their foraging area. Note that Norway rats like to hoard food so they may relocate baits.
General Sanitation Tips
Sanitation is critical in rodent control. Pest populations will increase to meet resource levels; sanitation is in fact good rodent management. Selection of landscaping and management of exterior areas to eliminate clutter, debris, and food refuse are essential for all school campuses. Proper management of dumpsters can impact rodent populations. Rodents depend on food, water and harborage in order to survive and schools provide adequate levels of all three items.
Clutter control has varying levels of consequences relative to impacting rodent infestations depending on the site. A cluttered closet inside a classroom can harbor several families of mice. Therefore, managing clutter on a school campus can make all the difference in a rodent control program. Cardboard and lose paper should be limited. Food items should be stored in locking rubberized containers or glass jars. In food storage areas, inspection isles should be made so that the pest management professional can see behind food items to see evidence of rodent activity.
Trapping Tips
Both the roof and Norway rat are leery of new things in their environment, so traps should be in place for several days before being set. After being set, they should remain in place for a week before being moved to a new location. Traps should be set along rodent runways to be most effective. The trigger side of the trap should be on the wall side. Because large rodents may move traps, all traps in a school should be secured, even if traps are set on weekends or during holidays.
Baiting Tips
Rodent populations may have a food preference for a variety of items. They may be feeding on ketchup packages, bread, candy bars or fruit. If that is the case, you may use those items for bait. Generally, roof rats prefer fruit and nuts, and Norway rats prefer fish (sardines) or meat. Other baits include chocolate or dry oatmeal. Peanut butter works as a bait for both rats, but peanut allergies of the building inhabitants should be considered. You may want to use multiple baits to provide a variety of choices. For instance, you may set several traps with chocolate, several with peanut butter (or meat), and several with dry oatmeal. Another tip is to “bait” some traps with cotton balls or a ball of string. Pregnant females will scavenge for these items to make a nest.
| Location /Situation | Suggested thresholds | Nonchemical Control Options | Preferred Chemical Treatment(s) |
|---|---|---|---|
| Cafeteria. | One rat justifies setting traps, improving sanitation, and rodent proofing the building. | Sanitation and clutter control will do a great deal to manage rodents. | Rodenticides should not be used indoors as it can result in rodents dying inside walls and ceilings, where odors prevail. Outdoors—rodenticides can be used, but should be placed in a tamper-resistant bait station and secured to a concrete block. Boxes should be checked at least monthly and bait replaced to avoid staleness in the bait. |
| Food Storage Areas. | See above. | Exclusion (rodent proofing) the building with hardware cloth, or concrete patches. | See above. |
| Gymnasiums. | See above. | Identify runways by rub marks, urine trails, or by using a thin layer of talcum powder. | See above. |
| Concession Stands. | See above. | Secured snap traps set at right angles to rodent runs. Traps should be checked often. Note: Traps should not be set where children may contact them. | See above. |
